Pneumatic concentrator



Aug; 25', 1942;

E. FREEMAN 2,294,290

PNEUMATIC CONCENTRATOR Filed cm. 21, 1940 2 Sheets-511961. l

l! '5, 9 2 E. FREEMAN 2,294,290 v PNEUMATIC CONCENTRATOR Filed Oct. 21 1940 2 sheets-sheet;

[WE/W175,

Z'z/yE/vE EMMA/V Patented Aug. 25, 1942 UNITED STATES PATENT OFFICE PNEUMATIC CONCENTRATOR.

Eugene Freeman, Chicago, 111.

Application October 21, 1940, Serial No. 362,084

5. Claims. 7 '(Cl. 209-139) The invention relates to improvements in concentrators and more particularly to a pneumatic concentrator intended for the separation of precious minerals or other valuable materials from dust-dry ores and embodying a novel arrangement of structural features adapting it to be extremely effective to a high degree through directional control of air streams.

An object of the invention is to provide a concentrator of the character referred to with novel means to control the volume and spread of dustdry ore delivered to a plurality of air-blast ducts embodied therein.

Another object is to provide, in a pneumatic concentrator, anovel arrangement of passageways, ducts, and by-passes for the automatic reworking of the dust-dry ores a plurality of times.

Another object is to provide the tailings spout and the millings by-pass of a novelly constructed concentrator with novelly arranged automatically actuated dual closures.

Another object is to provide a novelly constructed power operated feed mechanism for positively delivering dust-dry ore or millings to the air-blast ducts.

The foregoing and such other objects of the invention as may appear hereinafter as the description proceeds, will be more readily understood from a perusal of the following specification, in which reference is had to the accompanying drawings; wherein:

Fig. 1 is a diagrammatic view showing an ore processing apparatus incorporating the improved concentrators.

Fig. 2 is a vertical sectional view of a pair of concentrators, taken substantially on line 2-2 of Fig. 1, and showing parts in elevation.

Fig. 3 is an enlarged fragmentarytransverse sectional view of the dust-dry ore delivery control means.

Fig. 4 is a fragmentary longitudinal sectional view of the means shown in Fig. 3, with parts in elevation.

Various types of pneumatic concentrators have heretofore been devised to effect, with a limited degree of success, the separation of precious minerals such as gold, mica, etc., from crushed or pulverized ores, utilizing the difference in a spe: cific gravity of the various particles of said ore. Known concentrators, however, are inefiicient primarily because they lack suitable means to effect reworking of the middlings a plurality of times, consequently, a high percentage of the precious mineral sought to be concentrated never recovered but instead is discharged with the tailings and lost.

The instant apparatus is mechanically designed to effect reworking of the material three times prior to its discharge. Before entering into a detailed discussion of the essential structural features of the concentrator per se. a brief outline of an ore treating apparatus as a whole is advisable.

In the apparatus selected for illustration and best shown in Fig. 1, broken ore is delivered into a hopper or other receptacle ll, containing any practical crushing mechanism l2 for reducing said ore to a substantially dust-dry substance. Said substance is discharged from the crusher into a duct l3 and conveyed to a conventional cyclone separator It. Any insufficiently crushed pieces of ore are discharged from the separator through spout l5 into the lower end of an endless bucket conveyor or elevator l6. As shown. the elevator carries said pieces upwardly and deposits them in the hopper II for recrushiug. The dust-dry ore ejected from the separator ll is carried through a conduit ll for uniform distribution and discharge, through several outlets it, into the respective hoppers IQ of a plurality of concentrators 2|. It should be understood at this time that only one concentrator may be used and that more than the five concentrators shown may be arranged in a bank as illustrated. If desired, the concentrators may be constructed in pairs as best shown in Fig. 2 to minimize space. Inasmuch as the two concentrators shown in Fig. 2 are identical, the path of the material through and the structure of but one of said units will be attempted.

Dust-dry ore discharged into the hopper I! (Fig. 2) from the supply outlet i8 is delivered into a restricted passageway 22 preferably in the form of a thin uniformly spread stream or sheet by providing, between said hopper and said passageway, suitable power operated means for controlling the flow thereof.

As best illustrated in Figs. 3 and 4, said control means preferably includes a substantially smooth surfaced roller 23 having a plurality of longitudinal spaced circumferential grooves 24 therein providing passageways or carriers for the dustdry material. The roller 23 is carried on a driven shaft 25 which, as shown in Fig. 1 may be common to all-of the rollers in all of the concentrators. Rotation of the roller 23 in a counterclockwise direction carries the material down into the passageway 22. Any material tending to is pack, clog or otherwise remain in any of the grooves 24 is forcibly ejected by fingers 24a which extend one into each groove. The fingers 240. preferably are located, with respect to the roller, at a point substantially beyond the vertical diameter thereof.

The thin, evenly distributed stream of material passing out of the passageway 22 enters a substantially vertically disposed duct 26 at a line spaced above the lower end thereof. The duct 26 constitutes a part of the air circulating passageways in the concentrator and is adapted to have an aireblast created therein upon the operation of a suitable exhaust fan 27 arranged at one end, as shown in Fig. 1, of a horizontal header 28 having a plurality of branches 29 opening therefrom and communicating one with each concentrator. The vertical air-blast duct 26 has its upper portion curved, as at 3|, and terminates in a substantially horizontal portion 32, preferably having a cross-sectional area slightly larger than the cross-sectional area of the duct. The inner or free end 33 of th horizontal portion 32 curves upwardly and terminates in a further enlarged chamber 34, having communication with the air exhaust pipe 29.

It should be apparent that upon operation of the exhaust fan 21, air is drawn into the lower open end of the vertical air-blast duct 26 and moves with great rapidity upwardly and then horizontally into further enlarged chamber 34 and out through the pipe 29. The upwardly moving air stream obviously entrains the finer particles (middlings) of the dust-dry material, discharged into the duct 26, upwardly; and the heavier particles, which constitute the precious minerals or other material to be concentrated, drop by gravity against the upwardly moving air stream into a receiver 35. Although the receiver 35 is shown as a pan or other receptacle, it should be understood that any suitable receiving means may be provided such as, for example, a belt conveyor for carrying said materials to a desired destination.

Experimentation has established that this single treatment of the dust-dry ore by an airblast stream is not entirely satisfactory due primarily to the fact that in the crushing operation many particles of precious metals or other materials are broken down to such a degree as to be of different specific gravity than the particles initially removed by said stream. As a consequence, unless the material or middlings is again subjected to further air-blasts or otherwise processed, such fine or broken down particles of precious material contained therein cannot be recovered. Accordingly, the bottom wall 36 of the chamber 34 is suitably inclined downwardly and terminates in a substantially vertical passageway 31, the lower angularly disposed end of which communicates with the interior of a second substantially vertical air-blast duct 38. Consequently, the middlings, entrained into the enlarged upper chamber 34 settle, due primarily to the decreased velocity of the air stream, and are conveyed downwardly by gravity in the passageway 31.

To prevent interference with the directed flow of air through the various parts of the concentrator, such as would be occasioned should a reverse draft or back wash be created in the pas sageway 31, a feed roller 23a, of substantially the same construction asthe feed roller 23 previously described, is providedadjacent to the lower end of said passageway 31. Although the feed roller 230 may be driven in any suitable manner, it is preferable that its shaft 39 carry a pulley 4| to receive a belt 42 which also is trained over a pulley 43 on the driven shaft 25. In this manner both rollers 23 and 23a are operated in unison from a single source of power.

The lower end of the second vertical air-blast duct 38 opens into the receiver 35 and its upper end terminates in a curved portion at opening into a second substantially horizontal portion 35. The bottom wall of the horizontal portion 35 is depressed angularly to provide a relatively large settling chamber 45 having a by-pass 31 leading therefrom and terminating substantially above the crushed ore receiving hopper 19.

The end of the chamber 35 inwardly of the settling chamber 48 terminates in a vertical branch, the downwardly extending portion of which constitutes a tailings chute 48 and the upwardly extending portion 69 of which curves forwardly and opens into the upper chamber 34 of the concentrator. These various duct portions and passageways connecting the vertical I air-blast duct 38 with the upper chamber 34 provide a tortuous path for the air-blast obviously created therein upon operation of fan 21. Consequently, the lighter particles of the middlings deposited into the air-blast stream in the second air-blast duct 38 are entrained upwardly into the associated horizontal chamber 85. The heavier particles, which constitute the precious minerals drops down into the receiver 35.

Due to the relative large area of the chamber 45 and its companion settling chamber 48, the air stream loses a considerable amount of velocity and a major portion of the middlings entrained therein drop into the settling chamber and are conveyed through the by-pass 47 into the hopper IQ for reworking. Such particles of dust remaining in the air stream are deposited into the tailings chute 48. Entrainment of any of the tailings into the upper portion 49 is efiectively prevented by angularly disposed baifies 5| arranged in the position substantially as shown, whereby such tailings are mechanically separated from said air stream and drop into the chute by gravity. Similar baflles 52 also preferably are arranged adjacent the inlet of the air exhaust pipe 29, thus insuring the delivery of all middlings carried into the chamber 34 to the second air-blast duct 38.

The apparatus described obviously is such that the degree of removal of precious materials from the dust-dry ore is very high primarily because said material is worked and reworked at least three times. In other words, precious mineral is removed upon initial treatment in the air-blast duct 26. The middlings are then reworked in the second air-blast duct 38 to eifect removal of much of the remaining precious minerals and finally should any precious mineral remain in that portion of the so called tailings, carried through the by-pass 41 into the hopper Is all or at least a greater portion thereof is quickly and eiiiciently removed upon being again carried through the multiple stages of concentration.

Tailings discharged into the chute 48, drop into the lower or discharge end 53 thereof. It is essential, however, that said end 53 normally be. closed to prevent a back-wash and at this end a pair of jointly actuated gates 5454a are provided each of which carries a pivotally mounted rack bar 55 for associate engagement with an idler pinion 56. The gates 54--54a are actuated only by the weight of an accumulation of tailings therebehind. An accumulation behind the inner gate Ila opens said gate and the tailings pass into the space between said gates. When the inner gate Ila opens, the outer sate 54 closes, due to the pinion and rack connection therebetween. As soon as the accumulation of tailings behind the outer gate 54 issuiilcient, said gate opens automatically and the inner gate closes. A similar arrangement is provided on the end oi. the by-pass 41 and like numbers are used to identify corresponding parts.

The intensity of the flow of air through the ore ducts 26 and 38 may be manually controlled by-suitably disposed adjustable baflles 51 provided in the curved portions 3| and 44 respectively thereof, which baflies are adjusted upon manipulation of control levers II and I59 respectively.

Although an exemplary arrangement has been illustrated in the accompanying drawings and described in the foregoing specification, it is to be understood that the disclosure is illustrative and not restrictive, and that the apparatus may embody a variety of modifications in detail structure without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a concentrator, the combination with two air-blast ducts each having a vertical and a horizontal portion, said horizontal portions being disposed one above the other, means including a hopper for delivering dust-dry material into the vertical portion of one of said ducts, said ducts being open on their lower ends, common means for supplying a stream of air through the concentrator to create an air-blast in both ducts to entrain the lighter particles of material in said one duct upwardly into the upper horizontal portion, a convolute passageway connecting said horizontal portion with the vertical portion of the other air-blast duct, said passageway including a portion having an enlarged cross-section, means in said enlarged portion to separate the particles from the air stream, said particles being delivered into the air-blast within said duct whereby the lighter of said particles are entrained upwardly into the lower horizontal portion, said lower horizontal portion including a settling chamber and terminating in a tailin'gs spout having an air stream outlet conmiunicating with the enlarged portion of the convolute passageway, and a by-pass connecting the settling chamber with the hopper to convey by gravity any remaining heavier particles to said hopper for reworking.

2. In a concentrator, the combination with two air-blast ducts each having a vertical and a horizontal portion, means including a hopper for delivering dust-dry mineral bearing ore into the vertical portion of one of,said ducts, said ducts being open on their lower ends, means for supplying a current of air through the concentrator to create an air-blast in both ducts to entrain the lighter particles of ore in said one duct upwardly into its horizontal portion, said horizontal portion having a greater sectional area than the connecting vertical portion, a convolute passageway connecting said horizontal portion with the vertical portion of the other air-blast duct to deliver said lighter particles into the air-blast therein whereby the lighter of said particles are entrained upwardly into the second horizontal portion, said horizontal portion having a greater sectional area than its connecting vertical portion and including a and a by-pass connecting the settling chamber with the hopper to convey by ravity any remaining heavier particles to said hopper.

3. In a concentrator, the combination with two air-blast ducts each having a vertical and a horizontal portion, means including a hopper having a feed roller therein for delivering dust-dry material into the vertical portion of one of said ducts, said ducts being open on their lower ends, means for creating an air current through the concentrator to create an air-blast in the ducts to carry the lighter particles of material in said i one duct upwardly into its horizontal portion, a

convolute passageway including an enlarged chamber connecting-said horizontal portion with the vertical portion of the other air-blast duct,

said enlarged chamber causing a reduction in the velocity of the air stream to separate the particles therefrom prior to delivery of said particles into the air stream within said second air-blast duct whereby the lighter of said particles are entrained upwardly into the second horizontal portion, said portion including a settling chamber and terminating in a tailings spout, means to separate the tailings from the air stream, means directing said air stream through the enlarged chamber for exhaust with the air contained therein, and a by-pass connecting the settling chamber with the hopper tov convey particles in said settling chamber b gravity into said hopper for reworking.

4. In a concentrator, the combination with two air-blast ducts each having a vertical and a horizontal portion, means including a shopper having a feed roller therein for delivering dustdry material into the vertical portion of one of said ducts, said ducts being open on their lower ends, means for supplying a current of air' through the concentrator to create an air-blast in the ducts to entrain the lighter particles 0! material in said one duct into its horizontal portion, an enlarged passageway in communication with said horizontal portion, means in said passageway to separate the particles from the air stream, a conduit connecting said passageway with said second duct to convey said particles into said second duct, means in said conduit to prevent a reverse flow of air therethrough, the

vertical and a horizontal portion, controlled settling chamber terminating in a tailings spout,

means to deliver a uniform stream of dust-dry material into the vertical portion ofone of said passageways, single means for supplying a stream of air through the concentrator to create an air-blast in both passageways to entrain the lighter particles of material in the vertical portion of said one passageway upwardly intoits horizontal'portion, said horizontal portion being of greater cross-section than its vertical portion, a convolute passageway connecting said horizontal portion with the vertical portion of the other passageway, said passageway including a portion having an enlarged cross-section, bames in said enlarged portion to separate the particles from the air stream, said particles being deiivered by said convolute passageway into the air-blast within said other passageway whereby the middlings are entrained upwardly into the second horizontal portion having a greater crosssection than its vertical portion, controlled means in said convolute passageway to effect discharge of a uniform stream of particles into said second passageway, said second horizontal portion including a settling-chamber, a tailings l0 spout and a passageway for the air stream communicating with the enlarged portion of the convolute passageway, a by-pass connecting the settling chamber with the controlled delivery means to convey by gravity any remaining heavier particles to the first air-blast passageway for re-working, and the vertical portions of both air-blast passageways being open at their lower ends to discharge concentrated particles not entrained in said air-blasts.

EUGENE FREEMAN. 

